$\dfrac{18}{100} + \dfrac{4}{10} = {?}$
Answer: The fractions must have the same denominator before you can add them. Rewrite $\dfrac{4}{10}$ as $\dfrac{40}{100}$ $\dfrac{18}{100} + \dfrac{40}{100} = {?}$ $ = \dfrac{58}{100}$